Network distribution system



March 17, 1942. J. 5. PARSONS NETWORK DISTRIBUTION SYSTEM Filed March 30, 1939 INVENTOR zfohn 5. Parsons.

WITNESSES:

BY 2/ r M ATTO R'N EY Patented Mar. 17, 1%42' NETWGRK DISTRIBUTIQN SYSTEM John S. Parsons, Swissvale, Pa, assignor to Westinghouse Electric 62 Manufacturing Company, East Pittsburgh, Pa, a corporation of Pennsylvania Application March 30, 1939, Serial No. 264,931

17 Claims.

This invention relates to methods of relaying alternating-current network distribution systems and has particular relation to relay systems of the directional type for controlling the operation of network protectors or circuit breakers adapted to connect the load network to a feeder circuit.

As is well known, network protectors are interposed =between the transformers that step the high feeder voltage down to the low utilization voltage of the network, and feeder circuit breakers are interposed between the source of power and the feeder circuit. Directional relay equipment for controlling the operation of a network protector is effective upon the closing of a feeder circuit breaker to cause closing of the network protector if the magnitude and phase relation of the feeder voltage with respect to the network voltage are such that the protector will remain closed. In the event of a fault on the feeder or transformer, or upon the opening of the feeder circuit breaker, the directional relay equipment functions in response to the reversal of power flow, that is, power flow from the network to the feeder, to trip the network protector.

A form of directional relay equipment has been proposed which is normally insensitive but which is rendered sensitive upon the occurrence of a fault, such as a phase-to-phase or phase-toground fault, on the feeder. The terms sensitive and insensitive are purely relative, the former indicating, for example, that the directional relay equipment operates to trip the network circuit breaker in response to a relatively low reverse current such as 0.2% of the network protector rating, and the latter indicating that the relay equipment operates to trip the network circuit breaker only in response to a much higher reverse current. The purpose of the sensitiveinsensitive arrangement is to prevent unnecessary tripping of the network protectors in response to low reverse currents of short duration caused by regenerative equipment operating on the network, or switching operations in the net work.

In cases where a plurality of network protectors operate on the same feeder, it is possible that if the number of such protectors provided with sensitive-insensitive directional relay equipment is a high per cent of the total number of network protectors on the feeder, ground fault on any of the phase lines of the may fail to cause suficiently high reverse current to exceed the insensitive seJting of We relay equipment and thus fail to cause tripping of the network protectors on the feeder.

It is accordingly an object of my invention to insure the tripping of network protectors having a sensitive-insensitive directional relay control.

Another object is to control the operation of one or more network protectors from a remote point, such as at the source of power, in a novel manner.

The above objects, and other objects of my invention which will be made apparent hereinafter, are attained by means of an illustrative embodiment of my invention shown schematically in the accompanying drawing, in which:

Figure 1 is a diagrammatic view of protective equipment for a feeder on a distribution network system, and

Fig. 2 is a diagrammatic view of a distribution system having a plurality of feeders.

Referring to the drawing, Figure 1, there is shown a network protector or circuit breaker II for connecting the phase lines l2a, Nib and I20 of a polyphase network system E2 to corresponding lines i3a, Nb and I30 of a feeder circuit l3. A feeder circuit breaker I l having the usual automatic tripping control functions to connect the feeder lines to corresponding buses I5a, lib and I50 of the polyphase source of power 15 indicated as star-connected with grounded neutral. A bank of single phase step-down transformers or a polyphase transformer iii, hereafter called the transformer i6, is shown illustratively with the primary windings thereof connected in delta to the high voltage feeder lines and the secondary windings thereof connected in star, with grounded neutral, to the side of the network protector opposite that to which the network lines are connected.

The network circuit breaker H is provided, in conventional manner as indicated diagrammatically, with a closing mechanism including a m0- tor or solenoid I Hr, a trip mechanism including a latch i IL for holding the circuit breaker in closed position and a trip coil lit for tripping the latch to cause the circuit breaker to open. The network circuit breaker is also provided with a plurality of auxiliary contacts or switches Ha, 1 lb,

llc, lid and I Be, the first four of which are back contacts and the last contact He being a front contact. The auxiliary contacts lid and He are associated with the closing solenoid Hm and trip coil lit, respectively, in conventional manner.

sitive, and a phasing relay [9 adapted to cooperate with the directional relay H in controlling the operation of the closing solenoid iia: to close the network circuit breaker H.

A closing relay 2| of the self-holding type is preferably provided, as shown, to avoid the necessity of the contact members of relays I! and Iii carrying the energizing current for the closing coil Ha: of the network circuit breaker as well as to insure closing of the network circuit breaker. This relay may be adjusted to close its contacts only when the voltage of the feeder to which it is connected is high enough to assure positive closing operation of the closing solenoid or motor 1 Ir.

According to my invention, I have provided, in addition to the above equipment, a suitable voltage responsive device 22, such as an electrostatic relay, that operates in response to conditions on the high voltage feeder. The relay 2?. will be described and its operation explained in detail hereinafter. Briefly, however, the relay 22 is operatively responsive to abnormally high or abnormally low voltages impressed thereon due to ground faults on the feeder lines 13a, I31) and I30 for causing tripping of the network circuit breaker.

Considering the parts of the relay equipment in greater detail, the directional relay I1 is of the polyphase induction disc or drum type, such as shown and described in detail in my prior Patents No. 1,973,097 and No. 2,013,836. This relay comprises a rotary disc or drum element (not shown) with which three separate driving magnet cores (not shown) are associated. On each magnet core is wound a group of three windings, the three groups being designated respectively by the reference numerals 25, 25 and 27. The windings of each group comprise a potential winding, a current winding and a phasing winding indicated respectively by the reference numeral of the corresponding group with the sui'lixes e, i and 11. For example, the potential, current and phasing windings of group 25 are identified by the reference numerals 25c,

and 25p, respectively.

The rotary element of relay fl is adapted, upon rotation, to correspondingly rotate spindle l'l'a on which is carried in insulated relation a contact member HE). A torsion spring Ilc biases w the spindle in one direction to effect engagement of contact member ill; with a stationary closing contact member lid and yieldingly opposes rotary movement of the spindle and contact member llb in the opposite direction into engagement with a stationary trip contact member Hf that is effected in response to the torque exerted thereon by the three groups of windings.

The potential windings 25c, 25c and 276 are connected between the network lines lid, I22). lZc, respectively, and ground. The current windings 251', 251' and Eli are energize-d according to the degree and direction of flow of the current in the respective phase lines on the secondary or low voltage side of the transformer 56 by means of suitable current transformers Ma, 2% and 23c, respectively. The phase windings 25p, 26p and 27p are connected in parallel relation with corresponding bridging contact members of the network circuit breaker that are adapted to connect the phase lines on the secondary side of the transformer iii to the network lines I241, i212 and 320, respectively.

Included in series relation with the phasing windings 25p, 26p and 27p are phasing impedances shown as resistors 251*, 261' and 272', respectively. With the network circuit breaker in open position, as shown, the auxiliary back contacts Ha, lib and I I0 shunt a portion of the resistors 251", 261' and 271, respectively. When the network circuit breaker is closed, the auxiliary contacts Ha, lib and Ho are open, thus removing the shunt on the portion of the corresponding resistor and rendering the entire resistor effective to limit the current in the phasing wining to a low degree.

The three groups of current and potential windings of relay I! are so related that when power flows from the transformer it to the network l2, the torque on each of the driving magnets tends to maintain the movable contact member Ilb in contact with the closing contact member l'ld. When power flows from the network l2 to the secondary windings of the transformer E5, the torque exerted by the driving magnets tends to rotate the spindle Ha and the contact member llb so as to effect engagement of the contact member llb with the trip contact member 11 The phasing windings 25p, 26p and 27p are so related to the corresponding current and potential windings of relay I! that when the network circuit breaker II is open and the network 12 energized from other transformer banks (not shown), the torque exerted by each of the driving magnets tends to cause the movable contact member l'lb to engage the closing contact member Nd, if the transformer secondary voltage is in phase with the network voltage and exceeds the network voltage by more than a predetermined amount, such as a fraction of a volt. If the component of transformer secondary voltage in phase with the network voltage fails to excced the network voltage by the predetermined amount, the torque exerted by the driving magnets tends to cause the movable contact member ill) to engage the trip contact member Hf. A more extended and theoretical discussion of the operating characteristics of relay ll may be had by reference to my prior Patent No.

1,973,097, if desired. The above explanation is deemed suflicient for the purpose of the present invention, however.

The restraining relay [8 comprises a positive phase-sequence filter 3!, preferably of the type disclosed in Patent No. 1,936,797 to B. E. Leneban, and a voltage responsive relay 32 associated therewith in a manner to be energized in accordance with the positive symmetrical component of the phase Voltages on the secondary or low voltage side of the transformer l 6.

The filter 3! comprises an auto-transformer am having a tap 3H for providing a voltage less than half, for example, 40%, of the total voltage impressed on the auto-transformer from one phase on the secondary side of the transformer 16, and also a reactor 31:0 and resistor 31? connected in series relation across another phase of the secondary side of the transformer l5 and 3 having a combined lagging phase angle of the subscripts to the feeder lines I312, I31) and I30, the voltage impressed on the coil of the voltage responsive relay 32 is proportional to the positive phase-sequence symmetrical components of the phase voltages of the secondary windings of the transformer 16, as explained in detail in Patent No. 1,936,797 to B. E. Lenehan, mentioned above.

The coil 32s of the voltage responsive relay 32 is designed to actuate a movable contact 32%, to closed position in response to a positive sequence symmetrical component voltage in excess of a certain percentage, such as 95%, of the balanced phase voltages on the secondary side of the transformer l6 and to permit the contact 3211 to drop out to open position when the positive symmetrical component voltage is less than a predetermined minimum percentage such as 90% of the normal balanced phase voltages on the secondary side of the transformer 15.

When the voltage responsive relay 32 is actuated to its closed position, the contact member 321i connects the corresponding ends of three r sistors 32a, 32b and 320 to form an. artificial neutral point of a star connection. The opposite ends of the resistors 32a, 32b and 320 are con-- nected respectively to the several junctions between the respective phasing windings 25p, 25p, 21p of relay l1 and their associated phasing resistor 251", 257" and 211". responsive relay 32 in closed position, a threephase potentiometer is formed for applying a voltage component to each of the phasing windings of the relay ll.

With the phasing windings of relay i1 energized in this manner, a biasing or restraining torque is exerted by the driving magnets of the relay ll which maintains the movable contact member llb thereof firmly in contact with the closing contact member Md. The relay ll is accordingly conditioned thereby for insensitive operation. With the voltage-responsive relay in open position the three resistors 32a, 32b and 320 are disconnected at the artificial neutral point and the directional relay I! is accordingly con ditioned for sensitive operation.

The phasing relay I9 is preferably of the single element induction disc or drum type in which a driving magnet core is associated with the disc or drum and has wound thereon a phasing winding 19p and a potential winding IEic in the usual manner. The potential winding We is connected between one of the network lines, such as the line 12a, and ground in series with a resistor Mir for securing a rotated leading closing characteristic in a manner well known. The phasing winding I93) is connected in series with a suitable resistor |9r across the network circuit breaker contacts connecting the phase line on the secondary side of the transformer l 6 to the network line i242.

The rotary induction disc or drum of the phasing relay is adapted to rotate a spindle 39 in correspondence therewith, the spindle 39 having in insulated relation thereon a contact member 39a and being urged in a direction to cause the contact member 39a to engage a fixed contact member ll under the influence of a, torsion spring 42.

In order to avoid the necessity of the relatively delicate contact members of relays l7 and it carrying the current required to operatively energize the closing solenoid or motor l ir and insure positive closing of the network circuit breaker, the closing relay 2! is provided. As is apparent from the drawing, the operating coil Zia of clos- Thus, with the voltagefrom the normal voltage ima ing relay 2! is connected in series relation with the closing contact members Hat and M of relays l1 and I9, respectively, and auxiliary contact 1 id of the network circuit breaker II across two of the phase lines on the secondary side of the transformer I6. When operatively energized, the coil 2la actuates a contact member 25b into a closed position wherein it establishes a circuit for energizing the closing solenoid lirr of network circuit breaker I independently of the closing contact members of relays ll and I9 and at the same time establishes a holding circuit for the coil thereof to maintain it energized independently of the relays H and Hi. The circuit for energizing the closing solenoid Han and the holding circuit for the coil 2 la of the closing relay both include the auxiliary contact I Id of the network circuit breaker II and are deenergized by the opening thereof only after the network circuit breaker is definitely and positively closed.

The voltage responsive relay 22 which may be of the electrostatic type, comprises a suitably designed operating coil shunted by a circuit including a protective gap 5, and connected between one of the feeder lines on the high side of transformer it. shown at 53c, and ground as through a suitable coupling capacitor it. The coil 22a is so designed and adapted as to maintain a contact member 2% in intermediate or floating position out of engagement with and between two sets of three contact members when it is energized by the normal voltage im pressed thereon, namely the normal voltage between the feeder line l'ic ground. When the coil 22a is energized by a voltage which is in excess of a predetermined voltage, such as one that is proportional to la0% oi the normal voltage impressed thereon, it actuates the contact member 22b upwardly into engagement with the upper or over-voltage set of contact members ids, 45b, and 480. When the coil is energized by a voltage which is less than a voltage proportional to, for example, 38% of the normal voltage impressed thereon, the contact member 22b is biased into contact with the lower or under-voltage set of contact members Mia, 48b and 490.

Although the relay 22 may be replaced by an under-voltage relay which drops out when the voltage from the feeder phase conductor 0 to ground falls below 36% of its norn a]. value to connect the three contacts tea, iiib, ids, and an over voltage relay which picks up when the same voltage increases to a value over li of its normal value to the three contacts 48a, 68b, the floating type of relay appears simpler and preferable.

The movement of the contact member 22b in either direction out of its normal position is in hibited by suitable means, such as the dash pot 5i indicated, so as to de contact member 22?) with. ether set of its associated contact members for a predetermined time, such as one second, following change ressed on the coil 22a to a voltage in excess of the 1.46% maximum or below the 39% minimum. The urpose of this time delay will be explained 11 matter.

The contact members 18a, Mb a. d Mic are v the en agement of connected to the contact members 49a. 42b and 3c, respectively, as shown. In the upper and lower positions thereof, the contact member 22bconnects contact members @821 and or its and 4% to establish a branch connection in the circuit for energizing the trip coil 8 it or" the netis in parallel with the trip contact ii) of the relay :3, thus being effective to trip the network circuit breaker open independently of the trip contact ll of relay ll.

When the contact member connects contact members lfib and or contact members 432) and 253c, it establishes a shunt circuit in parallel with the operating coil 2 id of closing relay 2i and the closing contacts lid and 4| of the two relays ii and 53, respectively, thus preventing operation of the closing relay to enersize the closing solenoid or motor iirc of the network circuit -er H. The purpose of this shunt connection is to prevent pumping of the network circuit breaker H, should the coil of relay 22 fail under normal conditions with power being supplied over the feeder circuit 53 to the network it, as will be xplained in further detail later.

A resistor 53 is provided in series circuit relation with the closing coil Zia of relay 2! to limit the current in this circuit and prevent a short circuit when the coil Ella is shunted by the contact member 222') of relay 22 in either its overvoltage or under-voltage position.

The operation of the apparatus is as follows, assuming that the feeder and network circuit breakers M and ii are open, that the network I 2 is deenergizcd or dead and that the various relays and switch devices are in the positions shown.

When the feeder circuit breaker M is closed under manual control in well known manner, the feeder lines Ida, 53b and ltc are connected to the buses l5a, limb and ice of the source of power IE5 and the primary windings of the trans former or transformer bank it are energized. With the network circuit breaker ll open, no load current flows in the secc d ry windings of the transformer E6 although voltage is correspondingly developed on the phase lines leading from the secondary windings to the network circuit break-er ll. The voltage between each of the phase lines on the secondary side of the transformer l5 and ground is impressed on a circuit including in series relation, a phasing winding, phasing resistor and potential winding of one of the corresponding phase winding groups 25, 26 and 2'? of the direction relay H. For example, the phasing Winding p, phasing resistor 251', and potential winding 256 are connected in series relation between the a phase line on the secondary side of the transformer l5 and ground.

If no utilization devices or translating devices, that is, transformers in other feeder circuits for the network, are connected to the dead network I2, the current in each of the phasing windings 25p, 25p and Zip is in phase with the corresponding potential windings 25c, 26c and Ele, respectively, and the torque exerted on the rotary induction disc of the relay ll tending to shift it out of its normal position is small because of the quadrature space relation of the phasing and potential windings. If any utilization devices or translating devices are connected to the network l2, as is usually the case, they act as a partial short-circuit for the relatively high impedance potential windings 25c, 26c and 21a and thereby prevent the development of an appreciable dis placing torque on the rotary disc of relay H.

In either case, therefore, the biasing spring He maintains the movable contact member ill) in contact with the closing contact member llcZ of relay ll. Similar considerations apply to the work circuit breaker i i, which branch connection phasing relay I9 and the biasing spring 4-2 thereof maintains the movable contact member 39a in engagement with its associated stationary contact member 4|.

Inasmuch as the trip coil auxiliary switch lie of network circuit breaker I! is open, the a phase voltage of the secondary side of transformer I6 is not impressed across the reactor 3m and resistor 311 of the positive phase-sequence filter 3!. Thus the positive symmetrical component of the polyphase secondary system is below of the balanced phase voltage, and consequently the voltage responsive relay 32 is not actuated to closed position but rather remains in its open position shown.

With the movable contact members of the directional and phasing relays H and I 9 in contact with their respective closing contact members as just described, however, the circuit for energizing the operating coil Zia of closing relay 2| that extends from the c to the a phase line on the secondary side of transformer [6 by way of auxiliary switch lid of the network circuit breaker, is completed and the contact member 2| 1) thereof is accordingly actuated to its closed position for energizing the closing solenoid Hr of the network circuit breaker H and establishing its own holding circuit independently of the contact members of relays l1 and IS.

The network circuit breaker I is thus actuated to closed position and latched therein in response to the energization of the closing solenoid Hr. In its closed position, the network circuit breaker I l connects the phase lines on the secondary side of the transformer I8 to the corresponding phase lines of the network I2, thereby energizing the network. In the closed position of the network circuit breaker II, the trip coil auxiliary contact He closes the circuit lmpressing the a phase voltage of the secondary side of the transformer IS on the reactor 3 Ir and resistor 3 lr of the positive phase-sequence filter 3 l. The full polyphasc voltage of the transformer I5 is thus applied to the filter 3| and the voltage responsive relay 32 is accordingly actuated to closed position connecting the potentiometer resistors 32a, 32b and 32c in star. As previously explained, the directional relay I! is accordingly thereby conditioned for insensitive operation.

If a fault occurs on the network l2, it is burned clear in the usual manner. In the event that a fault occurs on the network comparatively close to the network circuit breaker so as to cause the voltage responsive relay 3?. to drop out, the network circuit breaker H nevertheless remains closed because the direction of power is still normal, that is from the feeder circuit to the network.

If a phase-to-phase or three phase fault occurs on the feeder lines Isa, l3?) and I30, the direction of power flow reverses and a considerable reduction in the voltage of one or more phases occurs, depending upon the nature of the fault. The positive symmetrical components of the polyphase voltage on the secondary side of trapa former [6 are accordingly reduced sutliciently to cause the voltage responsive relay to drop out and open the star connection of the potentiometer resistors 32a, 32b and 320. The directional relay 1'! is thus conditioned for sensitive operation and the movable contact ill: there f is cperated, in response to the reverse flow of power. into contact with the trip contact H to efiect energization of the trip coil Hi and the consequent opening of the network circuit breaker l l.

Assuming that the network If is energized by other transformer banks not shown, the potential windings 25c, 25c and The of directional relay I1 and potential winding Ille of the phasing relay I9 remain energized. As soon as the feeder circuit breaker It opens, in response to the operation of the usual overcurrent relay equipment (not shown), associated therewith, resulting from the fault current in the feeder lines, the voltage of the network i2 is impressed on the circuits of the phasing windings 25p, 26p and 21p of directional relay IT, as well as on the phasing winding I9p of phasing relay Id. With the network circuit breaker II open and the auxiliary contacts Ila, lib and He shunting a corresponding portion of each of the phasing resistors 251-, 261* and fl?" in series with the phasing windings 2510, 26,12 and 27p, respectively, an appreciable current now energizes the phasing windings of relay I! which, in cooperation with the potential windings results in a strong torque being exerted on the rotary disc of the relay IT to maintain the movable contact member Ilb in engagement with the trip contact member I'If. In a similar manner, a torque is exerted to hold the movable contact member Sta of the phasing relay out of engagement with its associated closing contact member 4!.

When the fault on the feeder circuit has been cleared or repaired and the feeder circuit breaker I4 again closed to restore the voltage on he feeder lines Ida, Ito and Ida, the movable contacts Ill; and 39a of relays I! and I9 are rotated into engagement with their respective closing contact members I'ld and ll and the network circuit breaker III is reclosed in the manner previously described, assuming of course the re quired phase-relationship and comparative magnitudes of the polyphase voltage on the secondary side of the transformer and on the .network I2. Just as previously described, the closure of the network circuit breaker II results in the impression of the polyphase voltage of the secondary side of transformer It on the positive phase-sequence filter 3| and the actuation of the voltage responsive relay 32 to closed position to condition the directional relay I! for insensitive operation.

If a ground fault occurs on any one of the feeder lines Ita, I31) and I3c, the reverse current may be sufficient to cause operation of the directional relay If to trip the network circuit breaker II. However, if a plurality of other network circuit breakers (not shown) are connected in parallel relation to the network circuit breaker II between the feeder lines I3a, I3?) and I30 and the network I2, the division of the reverse current among the plurality of network circuit breakers may be such that the reverse current through the individual network circuit breakers may be insuflicient to cause tripping operation of the directional relays therefor if all or a large number of them are conditioned for insensitive operation in the same manner as is directional relay I'l.

With the voltage responsive relay 22 provided as previously described, the tripping of any and all of the network circuit breakers is, however, insured.

If a ground fault occurs on either of the feeder lines Isa or I32), the voltage impressed on the coil of the voltage-responsive relay increases approximately 73% since the phase-to-phase voltage of the source I is now impressed thereon instead of merely a phase-to-ground voltage.

In such case, the predetermined maximum overvoltage is exceeded and the contact member 2% of relay 22 is accordingly actuated upwardly into engagement with the upper or overvoltage set of contact members 53a, 48b and 48c thereof with a suitable time delay, of the order of one second, as previously indicated. This time delay is for the purpose of allowing suflicient time for the usual overcurrent relay protective equipment (not shown) associated with the feeder circuit breaker It to operate in response to the fault current to trip the feeder circuit breaker I4 open before any of the network circuit breakers, including circuit breaker I I on the feeder I3 can open.

With a fault on feeder I3 and all feeder breakers closed there will be a reduction in one or more of the source bus voltages and consequently a reduction in corresponding voltage or Voltages of all feeders. This might result in the opening of all network breakers II on both the faulty feeder and the good feeders if a time delay was not introduced in their tripping operation sufficiently long to permit the feeder breaker I4 on the faulty feeder 3 to open and relieve the low voltage condition on the good feeders.

When the contact member 2212 of voltage responsive relay 22 engages its upper set of contact members, it causes energization of the trip coil I It of the network circuit breaker II and the consequent opening of that breaker, in the manner previously indicated. At the same time, with the contact member 222) engaging its upper set of contact members, the operating coil 2Ia of the closing relay 2| is shunted, as previously explained. This effectively prevents reclosing of the first opened network circuit breaker, on a particular feeder, before all of the network circuit breakers on that feeder have tripped.

With both the feeder circuit breaker I4 and network circuit breaker II open, the voltage impressed on the operating coil 22a of the relay 22 decreases ultimately to zero and the contact member 221) is thus shifted into engagement with its lower set of contact members. Since the network circuit breaker II is already tripped open, the only effect of this operation of relay 22 is to maintain the shunt circuit around the operating coil Zia of the closing relay ZI.

When the ground fault on the feeder line ISa or I319 is cleared or the line repaired, the reclosing of the feeder breaker M and the consequent restoration of normal voltage on the operatingcoil of the relay 22 causes the contact member 222) to be shifted to its normal floating posi tion between and out of contact with the two associated sets of contact members, and effects the closing of the network circuit breaker II in the manner previously explained.

,If a ground fault occurs on feeder line Iilc, the voltage impressed on the operating coil 22a of relay 22 will drop below the predetermined minimum 30% of normal voltage and the contact member 221) will accordingly be shifted downwardly into engagement with its lower set of contact members 49a, 49b and 49c after a time delay of the order of one second. The feeder circuit breaker I4 and the network circuit breaker II are accordingly successively tripped open in the same manner just described for over-Voltage operation of the relay 22.

While the shunting of the operating coil 2Ia of the closing relay ZI by relay 22 may serve to prevent reclosure of the first opened network circuit breaker prior to opening of the other network circuit breakers on the same feeder and thus on some systems make it possible to omit the phasing relay IQ, the primary purpose of such shunting is to prevent pumping of the network circuit breaker H in the event that the operating coil 22a of the relay 1:- homes open circuited under normal conditions wherein power is being supplied over the feeder E3 to the network l2.

Assuming that the coil 22a of relay becomes open circuited under normal conditions, the con tact member 221) is shifted into engagement with its lower set of contac members and 490 just as for an under-voltage operation. The network circuit breaker i3 is thus immediately tripped open. However, the feeder circuit 53 remains energized, the relays ll and 53 would be effective to cause immediate reclosure of the network circuit breaker H but for the fact that the operating coil 2 id of closing relay is shunt ed by relay and can therefore cause operation of the closing relay ill to close the network circuit breaker ii. Pumpi g oi the network circuit breaker ii is thus prevented.

If desired, the voltage responsive relay may be employed to trip the network circuit breaker l l under remote control of the operator at the source it by artificially simulating ground fault on one of the feeder lines lilo, its or Thus, a manually operated or controlled switch 54 may be provided at the power source 55 for grounding feeder line 530, either through an impedance, shown as a resistor ,5 or solidly.

As above explained, the relay ll purposely made insensitive in order to make it ess sive to reverse currents occasioned by regenerative loads, such as regenerative elevators or other equipment. Sensitivity is restored to the relay by operation of the positive sequence relay IE3 which removes the restraint from the phasing windings when the positive sequence voltage drops below a predetermined value. This drop occurs on twoor three-phase feeder faults, but on a phase-to-grcund fault the positive sequence Voltage remains too high for the relay 9% to drop and remove the restraint from the master relay H. In its insensitive condition, the master relay l1 usually is unable to respond to the small reverse magnetizing current, and the circuit breaker H fails to clear the feeder ill from the network it.

By providing the ground relay 22, complete protection is afforded by the combination of relays. On twoor three-phase feeder faults, the master relay ll trips the circuit breaker 5! di rectly or after the relay 18 operates to sensitize the master relay. On phase-to-ground faults, the ground relay 2. operates directly to trip the circuit breaker ll. When the feeder breaker Hi is opened manually, operation of the switch it actuates the relay 22 for tripping the circuit breaker ll.

Because of the full use of both sets of tripping contacts on the relay 22, the feeder It may be normally ungrounded. The ground switch 54 need be actuated only when the feeder circuit breaker is manually tripped.

In Fig. 21, the distribution circuit it is sh wn in single line as energized through a plurality of the transformers it from the feeder circuit I 3 and from a second feeder circuit wl'iich may be connected to different sources or same source 45 through the circuit breaker. I l and a similar circuit breaker M. A protective responunit fill, which may be similar to the p equipment shown in Fig. 1, is provided each transformer Certain subject matter hereiclosed in my copending matured into Patent 2,162, 1939.

It is not my intention that the present inven tion be restricted to the specific s uctural detail arrangement of parts or circuit or nections set forth herein, as various omissions, additions or modifications may be effected witout dcpafing from the spirit of invention. I do not desire, therefore, to impose ary limiter-u ns on the scope of my invention except such as are required by the scope of the prior art.

I claim as my invention:

1. In an alternating-current network distribution system, feeder circuit having a plurality of conductors, a network circuit, a transformer having its primary windings energized from the feeder circuit lines and its secondary windii gs arranged to be connected to the network circuit, a network circuit br aker for connecting the secondary windings of the transformer to the network, means controlled according to the voltage between one of the feeder circuit conductors and ground and effective to cause opening of the circuit breaker whenever the controlling voltage exceeds a certain abnormal high voltage or reduces below a certain abnormal low voltage, means for inhibiting the operative response of the last said means to a control voltage in excess of the abnormally high voltage or below said abnormally low voltage to delay the opening of the circuit breaker for at least a certain predetermined time, and means responsive to the direction of power flow through said circuit breaker for tripping said circuit breal er.

2. In an alternating-current network distribution system, a feeder circuit having at least two conductors, a network circuit, means including a transformer and a network circuit breaker for establishing a connection whereby power is normally supplied from said feeder circuit to said network circuit 11 operatively responsive to a reversal of pol-1e to effect opening of said net-- work circuit breaker, means controlled according to the vol 0 between one of said feeder conductors ground and operative independently of the lost said means to effect opening of the circuit breaker whenever the voltage 1 ween said one feeder conductor and ground varies an abnormal amount from its normal value.

In an ale 1atlng-current network distribution system, a feeder circuit having a plurality of conductors, a n" work circuit, a network circuit breaker for establishing a connection whereby power is normally s'u lied from said feeder circuit to said network circuit, means effective upon energization of said feeder circuit to cause said network circuit breaker to close, means Elective upon a reversal of power to cause said network circuit breaker to open, and means controlled according to the voltage between one of said feeder conductors and ground and effective independenly of he last said means to cause opening of said circuit breaker whenever the voltage between said one feeder conductor and ground varie an abnormal amount from its normal value.

4. In an alternating-current network distribution system, a feeder circuit having a plurality of conductors, a network circuit, a network circuit breaker for establishing a connection whereby power is normally supplied from the feeder circuit to the network circuit, means including a switch operatively responsive to a reversal of power for causing the circuit breaker to open, and means, including a switch connected in parallel relation to the switch of the last said means, operatively responsive to an abnormal variation from the normal voltage between one of the said feeder conductors and ground for also causing opening of said circuit breaker.

5. In an alternating-current network distribution system, a feeder circuit having a plurality of conductors, a network circuit, a network circuit breaker for establishing a connection whereby power is normally supplied from said feeder circuit to said network circuit, means operatively responsive to a reverse flow of power from the network circuit to the feeder circuit for causing the network circuit breaker to open, and means controlled according to the voltage between one of the feeder conductor and ground, said last means having a certain normal position in response to the normal conductor-to-ground voltage, being operated out of its normal position to one abnormal position after the expiration of a predetermined time delay whenever the conductorto-ground voltage exceeds a predetermined abnormal high voltage, and being operated out of its normal position to a second abnormal position after a predetermined time delay whenever the conductor-to-ground voltage reduces below a predetermined abnormal low voltage, and effective in either said one or said second abnormal positions to cause opening of the circuit breaker independently of said reverse power responsive means.

6. In an alternating-current network distribution system, a feeder circuit having a plurality of conductors, a network circuit, a network circuit breaker for establishing a connection whereby power is normally supplied from the feeder circuit to the network circuit, means effective in response to the energization of the feeder circiut for causing said network circuit breaker to close and thereby establish the connection wl'iereby power is supplied to the network circuit, means effective in response to a reverse flow of power from the network circuit to the feeder circuit for causing said network circuit breaker to open independently of any other system condition, and means controlled according to the voltage between one of said feeder conductors and ground and effective to prevent closing of the network circuit breaker by the said closing means, unless the conductor-to-ground voltage is with in a predetermined range of minimum to maximum values.

7. In an alternating-current network distribution system, a feeder circuit, a network circuit, a network circuit breaker effective when closed to establish a connection whereby power is supplied from said feeder circuit to said network circuit and when open to interrupt such supply of power, means for tripping said circuit breaker, electroresponsive means conditioned according to the relation of the voltages on the feeder circuit and the network circuit for effecting the closing of said circuit breaker, said electroresponsive means being independent of said tripping means, means for shunting said electroresponsive means to render it ineffective to cause closing of the circuit breaker when said system is not in proper operating condition, and impedance means for restricting the current flowing in said shunting means.

8. In an alternating-current network distribution system, a polyphase feeder circuit having a plurality of conductors, a polyphase network circuit, a network circuit breaker effective when closed to establish a connection whereby power is normally supplied from said feeder circuit to said network circuit, a polyphase power-directional relay, a phasing rel y, a closing relay, said power-directional and phasing relays cooperating to cause operation of the closing relay to effect closing of said circuit breaker, and means controlled in accordance with the voltage between one of said feeder circuit conductors and ground for rendering said closing relay inoperative under the control of said directional and phasing relays unless the voltage between said one feeder circuit conductor and ground is within a certain range of values.

9. In an alternating-current network distribution system, a feeder circuit having at least two conductors, a network circuit, means including a transformer and a network circuit breaker for establishing a connection whereby power is normally supplied from said feeder circuit to said network circuit, means operatively responsive to a reversal of power to effect opening of said network circuit breaker and normally ineffective for a small reversal of power, and mean controlled according to the voltage between one of said feeder conductors and ground and operative independently of the last said means to effect opening of the circuit breaker whenever the voltage between said one feeder conductor and ground varies an abnormal amount from its normal value.

10. In an alternating-current network distribution system, a feeder circuit having at least two conductors, a network circuit, means including a transformer and a network circuit breaker for establishing a connection whereby power is normally supplied from said feeder circuit to said network circuit, means operatively responsive to a reversal of power to effect opening of said network circuit breaker and normally ineffective for a small reversal of power, means responsive to a symmetrical component of an electrical quantity present in said system for increasing the sensitivity of said opening means, and means controlled according to the voltage between one of said feeder conductors and ground and operative independently of the last said means to effect opening of the circuit breaker whenever the voltage between said one feeder conductor and ground varies an abnormal amount from its normal value.

11. In an alternating-current polyphase network distribution system, a feeder circuit having a plurality of conductors, a network circuit, means including a transformer and a network circuit breaker for establishing a connection whereby power is normally supplied from said feeder circuit to said network circuit, means operatively responsive to a reversal of power to effect opening of said network circuit breaker, and normally restrained against operation for a small reversal of power, a positive sequence voltage filter connected for energization from said system, means responsive to a decrease in the output of said positive sequence voltage filter for removing said restraint, and means controlled accordingto the voltage between one of said feeder conductors and ground and operative independently of the last said means to effect opening of the circuit breaker whenever the voltage between said one feeder conductor and ground varies an abnormal amount from its normal value.

12. In an alternatingcurrent network distribution system, a polyphase feeder circuit having a plurality of conductors, a polyphase network circuit, a network circuit breaker effective when closed to establish a connection whereby power is normally supplied from said feeder circuit to said network circuit, a polyphase powerdirectional relay, means controlled according to a symmetrical component of the polyphase volt age on the feeder circuit for rendering said power-directional relay unresponsive except to a reversed power current exceeding a certain value as long as the symmetrical component exceeds a certain value and responsive to a reversed power current less than said certain value when the symmetrical component is less than the said certain value therefor, said power-directional relay being effective when operated in response to reversed power to cause opening of said circuit breaker, and means controlled in accor ance with the voltage between one of said feeder circuit conductors and ground, effective in response to the variation from the normal control voltage therefor resulting from a ground fault on any of said feeder circuit lines for causing said circuit breaker to open independently and regardless of operative response of the powerdirectional relay to power reversal,

13. In a polyphase network distribution system, a source of polyphase electrical energy, a polyphase feeder circuit breaker, a polyphase feeder circuit operatively connected to said source through said feeder circuit breaker, said feeder circuit being normally ungrounded in any position of said feeder circuit breaker, transformer means, a distribution circuit connected to said feeder through said transformer means, a circuit interrupter for disconnecting said distribution circuit from said feeder circuit, tripping means for said circuit interrupter including control means responsive independently to the deviation of a voltage difference between one conductor of said feeder circuit and ground 3GV8 and below a predetermined range of values for initiating a tripping operation of said circuit interrupter, means for closing said circuit interrupter, and means controlled by said tripping control means for rendering said closing means ineffective as long as said tripping control means is in tripping condition.

14. In a polyphase network distribution. system, a source of polyphase electrical energy, a polyphase feeder circuit breaker, a polyphase feeder circuit operatively connected to said source through said feeder circuit breaker, said feeder circuit being normally ungrounded in any position of said feeder circuit breaker, transformer means a distribution circuit connected to said feeder through said transformer means, a circuit interrupter for disconnecting said distribution circuit from said feeder circuit, tripping means for said circuit interrupter including control means responsive independently to the deviation of a voltage difference between one conductor of said feeder circuit and ground above and below a predetermined range of values for initiating a tripping operation of said circuit interrupter, said tripping means being effective only after the expiration of a predetermined time from the occurrence of said deviation, means for closing said circuit interrupter, and means controlled by said tripping control means for rendering said closing means ineffective as long as said tripping control means is in tripping condition.

15. In a polyphase network distribution systom, means for supplying electrical energy, a plurality of feeder circuit interrupters, a plurality of feeder circuits each connected to said means through one of said circuit interrupters, each of said circuit interrupters having means for tripping the interrupter in response to faults occurring on its associated feeder circuit, a distribution circuit, a plurality of transformers for connecting each of said feeders to said distribution circuit, a circuit breaker for each feeder circuit for operatively disconnecting the associated feeder circuit from said distribution circuit, means for tripping one of said circuit breakers responsive to the direction of power flow therethrough, and means for tripping said one of said circuit breakers responsive to a deviation of the voltage difference between one of the conductors of the feeder circuit for said one circuit breaker and ground from a predetermined range of values, said last-named tripping means being effective only after the expiration of a predetermined time following the occurrence of said cleviation.

16. In a polyphase network distribution sys tern, means for supplying electrical energy, a plurality of feeder circuit interrupters, a plurality of feeder circuits each connected to said means through one of said circuit interrupters, each of said circuit interrupters having means for tripping the interrupter in response to faults occurring on its associated feeder circuit, a distribution circuit, a plurality of transformers for connecting each of said feeders to said distribution circuit, a circuit breaker for eacl feeder circuit for operatively disconnecting the associated feeder circuit from said distribution cir cuit, means for tripping one of said circuit breakers including tripping control means responsive to a deviation of the voltage difference between one of the conductors of the feeder circuit for said one circuit breaker and ground from a predetermined range of values for initiating a tripping operation of said tripping means, said tripping means being effective only after the expiration of a predetermined time following the occurrence of said deviation, means for closing said one circuit breaker, and means controlled by said tripping control means for rendering said closing means ineffective when said tripping control means is in tripping condition.

17. In a polyphase network distribution systern, a feeder circuit, transformer means, a distribution circuit connected for energization from said feeder circuit throug said transformer means, a circuit interrupter for operatively disconnecting said distribution circuit from said feeder circuit, insensitive means responsive to reverse power for operating said circuit interrupter, means for increasing the sensitivity of said insensitive means responsive to the positive sequence voltage in said system, and means for operating said circuit interriupter on the occurrence of a conductor-to--ground fault on said feeder circuit.

JOHN S. PARSONS. 

